Hexosaminidase (HEX) deficiency causes several neurological disease phenotypes including spinal muscular atrophy and an ALS- like disorder in adults, cerebellar ataxia in children, and in infants dementia, seizures, and retinopathy. At least three gene loci are required for full HEX activity and defects at each can cause disease. This project is focused on defining the specific gene defects and peptide defects in our large group of patients with HEX deficiency disease. For the most part we will study patients' fibroblasts in culture. We have transformed with SV-40 a large group of HEX deficient patients' fibroblasts cultured from skin. Defects of regulatory genes cannot be easily studied in humans at present. Therefore, we have turned to the best available mammalian system, inbred mice, to study HEX regulation, especially temporal regulation, which may be important for some of our late-onset HEX deficient patients. We plan to compare HEX cDNA sequences and later genomic sequences from two inbred mouse strains which show genetically determined differences in HEX expression. We are taking advantage of four new tools which we have developed: 1. A new system for study HEX regulation, 2. A new method of peptide mapping using in situ CNBr cleavage, 3. Anti-HEX beta subunit monoclonal antibodies we recently raised, so far as we know the first anti-HEX monoclonals made, 4. A unique HEX beta-gene sequence which we recently cloned and have characterized.